DOI: 10.1615/TSFP4
LARGE EDDY SIMULATION OF SEPARATION FROM A THREE-DIMENSIONAL HILL AND COMPARISON WITH SECOND-MOMENT-CLOSURE RANS MODELLING
SINOPSIS
LES solutions for the flow separating from a three- dimensional hill in a duct are reported and compared to experiments and second-moment-closure RANS computations. The study was motivated by the observation that even the most elaborate turbulence models, based on non-linear eddy- viscosity formulations and second-moment closure, fail to give a satisfactory representation even of some gross features observed in experiments for the flow at a Reynolds number of 130,000, based on hill height. The comparisons in this study are for the experimental geometry, but at two Reynolds numbers, 13, 000 and 130,000, the former enabling better resolution than the latter. Also explored, for the lower Reynolds number, is the sensitivity of the LES solution to the spectral representation of the inflow, found to be substantial. For the lower Reynolds number, the RANS and LES solutions are close. For the real value, however, major differences arise, and the LES solution, on a grid of over 9M cells, also differs greatly from the experimental measurements. In particular, separation is predicted to occur too early, and the extent of the recirculation zone is excessive.